Disclosed in the embodiments herein is an improved system for separating and individually feeding sheets, especially print media paper sheets of varying sizes and weights, more reliably from a stack of sheets, with an improved, variable position, stack edge pneumatic fluffer.
By way of background, the use of stack edge fluffers or air knives to help separate and/or levitate sheets for improved sheet separation and feeding is an extensively developed art, with numerous patents. The following are noted by way of some recent examples of Xerox Corp. U.S. patents with disclosures of such systems, and for other such art cited therein: U.S. Pat. No. 6,186,492 issued Feb. 13, 2001 to Dechau, et al; U.S. Pat. No. 6,264,188 issued Jul. 24, 2001 to Taylor, et al; and U.S. Pat. No. 6,352,255 issued Mar. 5, 2002 to Taylor. Said U.S. Pat. No. 6,186,492 also discloses an example of a reciprocating vacuum feed head or xe2x80x9cshuttle feeder,xe2x80x9d with which the present embodiment may be desirably combined, but is not limited thereto. Sheet fluffers may also be combined in the same sheet separator/feeder system with what may be alternatively called xe2x80x9cair knivesxe2x80x9d blowing against at least the upper portion of the front, feeding out, or downstream edge of the stack in coordination with the individual sheet acquisition and feeding. Stack fluffing and/or vacuum sheet feeding is particularly desirable for higher speed printing systems, for providing more reliable high speed sheet separation and feeding and also for reduced marking or scuffing of sheet surfaces as compared to xe2x80x9cfriction retardxe2x80x9d or other such sheet separator/feeders which are more commonly used on slower, lower cost, printers.
As used herein, the term xe2x80x9cprintersxe2x80x9d will be understood to broadly include copiers, printers, multifunction devices, etc., with xerographic, ink jet, or other print media printing systems. The term xe2x80x9csheetxe2x80x9d as used herein refers to various print media sheets, of various sizes and weights, typically relatively thin, flexible or even flimsy paper, and sometimes even plastic (such as for overhead transparencies).
As is well known in the art, separating individual print media sheets from a stack of sheets reliably, with a very low rate of misfeeds or double-feeds, which can xe2x80x9cjamxe2x80x9d the printer, is difficult. Paper sheets may have variable sizes, variable curl, variable moisture content, variable thickness, variable weight, variable beam strength, variable surfaces, e.g., glossy or calendared, variable friction, etc. The sheets may even be xe2x80x9cedge weldedxe2x80x9d together from their stack size cutting or brake operation. It may also be desirable to acquire and feed smaller sheets even faster than larger sheets to reduced pitch space between sheets and effectively increase the print rate. Also, sometimes partially preprinted sheets are loaded into an input sheet feed tray from overprinting or duplex (opposite side) printing. Such sheets may have toners, inks or fuser oils on them, or induced curls, further changing their properties and posing additional separation and feeding challenges.
It will also be appreciated that various types of variously slide-mounted or otherwise movable stack edge guides are well known in the art, for various sheet stacking trays, and need not be described in any detail herein. Such edge guides can be reset to the size of the stack of sheets currently being loaded into that tray generally confine the sheets between such guides. The stack side guides can also assist in linear sheet feeding of the sheets in the orthogonal feeding direction. One, or both, opposing side guides may be movable. If both side guides are moveable they may optionally be ganged for coordinated movement towards or away from one another by a rack and pinion connection, as is also well known. E.g., Xerox Corp. U.S. Pat. Nos. 5,511,771 and 5,946,527. This allows for a xe2x80x9ccenter registeredxe2x80x9d sheet feeding system instead of an xe2x80x9cedge registeredxe2x80x9d system. An xe2x80x9cedge registeredxe2x80x9d system is shown (modified) from FIG. 3 of Xerox Corp. U.S. Pat. No. 6,302,390, and as shown need only have one side guide. In a xe2x80x9ccenter registeredxe2x80x9d sheet feeding system in which the side guides are so ganged the operator resetting movement of one side guide automatically moves the opposing side guide.
A movable stack end guide may also be additionally provided in sheet feeding trays, opposite from the feed-out end of the stack, movable in the process direction. It may also be movable an angle thereto for substantially centering on the ends of different widths of sheet stacks, as in Xerox Corp. U.S. Pat. No. 6,302,390, the Xerox Corp. xe2x80x9ciGen3xe2x80x9d product, and FIG. 3.
A specific feature of the specific embodiment disclosed herein is to provide a sheet feeding system for separating and feeding individual print media sheets in a process direction from a variable size stack of print media sheets loaded into a sheet feeding tray having at least one stack side edge alignment guide movable for alignment with said variable sizes of stacks of print media sheets, which sheet feeding tray is in a machine drawer which is openable for said loading of said variable size stacks of print media sheets into said sheet feeding tray, and which machine drawer is closable to allow said and feeding of said individual print media sheets from said sheet feeding tray in said process direction, the improvement comprising a pneumatic stack edge fluffer system for pneumatically assisting said separating and feeding of said individual print media sheets from said sheet feeding tray in said process direction, said pneumatic stack edge fluffer system automatically operatively engaging a side edge of said variable size stack of print media sheets in said sheet feeding tray in variable positions when said machine drawer is closed, and said pneumatic stack edge fluffer system automatically operatively disengaging a side edge of said variable size stack of print media sheets in said sheet feeding tray when said machine drawer is open.
Further specific features disclosed in the embodiment herein, individually or in combination, include those wherein said engagement and disengagement of said pneumatic stack edge fluffer system is cooperative with said movement of said at least one stack edge alignment guide, and/or wherein said pneumatic stack edge fluffer system comprises a telescoping and spring loaded pneumatic manifold mounted in said machine and extending toward said edge of said variable size stack of print media sheets loaded into said sheet feeding tray, and/or wherein said pneumatic stack edge fluffer system includes an extension member extending out over a portion of the upper surface of said stack of print media sheets when said machine drawer is closed, and/or wherein, when said machine drawer is closed, said pneumatic stack edge fluffer system is automatically engaged by said at least one stack edge alignment guide to automatically maintain a preset operative spacing of said pneumatic stack edge fluffer system from the side edge of said stack of print media sheets irrespective of the repositioning of said stack edge alignment guide, and/or a sheet feeding method for separating and feeding individual print media sheets in a process direction from a variable size stack of print media sheets loaded into a sheet feeding tray having at least one stack side edge alignment guide movable for alignment with said variable sizes of stacks of print media sheets, which sheet feeding tray is in a machine drawer which is openable for said loading of said variable size stacks of print media sheets into said sheet feeding tray, and which machine drawer is closable to allow said separating and feeding of said individual print media sheets from said sheet feeding tray in said process direction, the improvement comprising pneumatically assisting said separating and feeding of said individual print media sheets from said sheet feeding tray in said process direction with a stack edge fluffer system by automatically operatively engaging a side edge of said variable size stack of print media sheets in said sheet feeding tray in variable positions with said stack edge fluffer system when said machine drawer is closed, and automatically operatively disengaging said pneumatic stack edge fluffer system from said side edge of said variable size stack of print media sheets in said sheet feeding tray when said machine drawer is open, and/or wherein an air deflector for said pneumatic stack edge fluffer system is automatically extended out over a portion of the upper surface of said stack of print media sheets when said machine drawer is closed, and automatically not extended out over a portion of the upper surface of said stack of print media sheets when said machine drawer is opened to automatically provide unobstructed loading of said print media sheets into said sheet feeding tray and/or wherein, when said machine drawer is closed, said pneumatic stack edge fluffer system is automatically engaged by said at least one stack edge alignment guide to automatically maintain a preset operative spacing of said pneumatic stack edge fluffer system from the side edge of said stack of print media sheets irrespective of the repositioning of said stack edge alignment guide.
As to specific components of the subject apparatus or methods, or alternatives therefor, it will be appreciated that, as is normally the case, some such components are known per se in other apparatus or applications, which may be additionally or alternatively used herein, including those from art cited herein. All references cited in this specification, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features, and/or technical background. What is well known to those skilled in the art need not be described herein.